EXPLAINER: What do tsunami warnings mean and how to respond

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The United Nations has designated November 5 as World Tsunami Awareness Day to promote preparedness for natural disasters.

This includes urging the public to participate in drills, runs, or walks along tsunami evacuation routes to help build resilience.

Philippine Institute of Volcanology and Seismology (PHIVOLCS) director Dr. Ma. Mylene Villegas urged the public to be aware of the natural signs that indicate a tsunami is coming.

"Mahalaga sa pag remind sa tao sa natural signs. Yan yung pag lindol, pag urong ng dagat, at yung tunog na maaring senyales na may pabalik na tubig," Villegas said during the World Tsunami Awarness Day press conference in Quezon City.

(It is important to remind the public about the natural signs that a tsunami may occur. That is the earthquake, the receding of the sea, and sounds that could signal returning water.)

She added that proper response should be implemented to ensure public safety.

Tsunami

PHIVOLCS defined tsunami as a "series of sea waves commonly generate by under-the-sea earthquakes."

Its height could be greater than 5 meters and can occur when an earthquake is shallow-seated and strong enough to displace parts of the seabed and disturb the mass of water over it.

Aimed at ensuring public safety, PHIVOLCS provided four-level tsunami advisory:

No Tsunami Threat (Green)

Under this advisory, a large earthquake was generated, but there is no tsunami generated by this event.

It could also mean that a tsunami was generated but will not reach the Philippines.

This advisory is issued for information purposes only and no evacuation is needed.

Sea Level Change Monitoring (Yellow)

When PHIVOLCS releases this advisory, it means that the agency will monitor the sea level changes and provide updates about it.

No evacuation order is in effect, but the public is urged to wait and listen for updates.

Minor Sea Level Dusturbance (Light Orange)

PHIVOLCS releases this advisory when minor sea level disturbance is expected in some coastal areas with wave heights of less than 1 meter above the expected ocean tides.

The public is advised to engage in the following actions:

• Stay away from the beach and avoid the coast.
• People whose houses are located very near the shoreline are advised to move farther inland.
• Boat owners in harbors or shallow coastal waters of the affected provinces should secure their and move away from the waterfront.
• Boats already at sea are advised to stay offshore in deep waters until further notified.

Tsunami Warning (Dark Orange)

Under this advisory, a destructive tsunami is generated with life-threatening wave heights.

According to PHIVOLCS, a destructive tsunami is expected to arrive at the Philippine coastline with wave heights of greater than one meter above the expected ocean tides.

During this time, immediate evacuation of coastline communities is strongly advised.

Boat owners in harbors, estuaries, or shallow coastal waters of the affected provinces should secure their and move away from the waterfront.

Boats already at sea are advised or to stay offshore until further notified. —VAL, GMA News